Preparation method of PET/LDPE (polyethylene terephthalate/low-density polyethylene) sea-island fiber

The invention relates to a PET/LDPE sea-island fiber preparation method, which comprises: (1) using PET as an island phase, using a mixture of LDPE and PAA-Fe3O4 as a sea phase, using a composite spinning assembly to prepare a nascent fiber, installing a magnetic field at a position from a guide plate, a distribution plate to a spinneret plate in the composite spinning assembly, the PAA-Fe3O4 distributed in the LDPE in the direction perpendicular to the melt flowing direction is distributed along the magnetic field to form linear distribution; and (2) the nascent fiber is drafted in a drafting medium and then dried to obtain the PET/LDPE sea-island fiber, and the drafting medium is water or an aqueous solution containing 0.2-1.0 wt% of electrolyte. A passage perpendicular to the fiber direction is constructed in the sea-island fiber, so that water molecules can penetrate through the sea phase to permeate into the island phase, the drafting temperature of nascent fiber is reduced, and the problem that the PET/